Many vending machines have refrigerated portions from which refrigerated or frozen foods can be vended. The basic refrigeration system consists of an evaporator and fan, compressor and condenser. There are many different system configurations currently in use for providing the necessary cooling. Some are permanently installed in the vending machine while others are designed to be removable for greater ease of servicing. Since spoilage of refrigerated or frozen items can occur quickly on failure of the refrigeration system it is essential to have the shortest down time possible to preserve the product. It is common with removable refrigeration systems to merely take a new system to the vending machine site and replace the defective unit and take the defective unit for repair. This tends to provide the shortest down time, but the amount of time necessary to make the substitution will, again, depend on the manner in which the system is configured and the difficulty of removal of the old system and installation of the new. Some such systems require partial disassembly of the vending machine to remove the system which prolongs the down time and enhances the possibility of spoilage of the items in the machine. A better approach used in prior art vending machines is a system which can be slid in and out of the vending machine and tends to self align the interconnecting duct work which is needed to introduce the cooled air into the refrigerated portion of the vending machine and to remove the spent warmed are therefrom. Such a machine is disclosed, for example, in U.S. Pat. No. 4,730,750, assigned to the same assignee as the present invention. In that machine there is provided a self-contained refrigeration unit which has duct work which engages mating duct work in the refrigerated portion of the vending machine such that when the refrigeration unit is slid into the bottom of the vending machine the ducts are aligned and, when engaged, seal between the two duct works. Alignment tracks on the floor of the vending machine help align the duct work from right to left. However, this system can be difficult to align from front to back so as to completely seal between the two duct works.
Another difficulty with prior art vending machines is in the area of the monetary unit where the customer inserts his or her money to make a purchase. Because there is limited space within the housing of a vending machine there are difficulties in mounting and servicing various components of the monetary system such as the bill validator, coin changer and microprocessors which control various functions of the vending machine. Security in this area is also a problem since the monitory system is a usual area for vandals to attempt to gain entry or "jackpot" the mechanisms.
A still further problem associated with some prior art vending machines, particularly those intended for outdoor use, is their inability to satisfactorily control the internal temperature of the machine within the food storage area. This is true whether the machine is vending refrigerated or frozen foods. One main reason for this is the use of a large glass front on the machines which causes substantial heat transfer, particularly from the sun, although in cold weather the transfer can be in the opposite direction from the inside to the outside of the food storage area.